 /*******************************************************************************
  * Copyright (c) 2004, 2005 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.core.runtime.preferences;

 import java.io.InputStream ;
 import java.io.OutputStream ;
 import org.eclipse.core.runtime.CoreException;
 import org.eclipse.core.runtime.IStatus;
 import org.osgi.service.prefs.Preferences;

 /**
  * The preference service provides facilities for dealing with the default scope
  * precedence lookup order, querying the preference store for values using this order,
  * accessing the root of the preference store node hierarchy, and importing/exporting
  * preferences.
  * <p>
  * The default-default preference search look-up order as defined by the platform
  * is: project, instance, configuration, default.
  * </p><p>
  * This interface is not intended to be implemented by clients.
  * </p>
  * @since 3.0
  */
 public interface IPreferencesService {

     /**
      * Lookup the given key in the specified preference nodes in the given order.
      * Return the value from the first node the key is found in. If the key is not
      * defined in any of the given nodes, then return the specified default value.
      * <p>
      * Immediately returns the default value if the node list is <code>null</code>.
      * If any of the individual entries in the node list are <code>null</code> then
      * skip over them and move on to the next node in the list.
      * </p>
      * @param key the preference key
      * @param defaultValue the default value
      * @param nodes the list of nodes to search, or <code>null</code>
      * @return the stored preference value or the specified default value
      * @see org.osgi.service.prefs.Preferences
      */
     public String get(String key, String defaultValue, Preferences[] nodes);

     /**
      * Return the value stored in the preference store for the given key.
      * If the key is not defined then return the specified default value.
      * Use the canonical scope lookup order for finding the preference value.
      * <p>
      * The semantics of this method are to calculate the appropriate
      * {@link Preferences} nodes in the preference hierarchy to use
      * and then call the {@link #get(String, String, Preferences[])}
      * method. The order of the nodes is calculated by consulting the default
      * scope lookup order as set by {@link #setDefaultLookupOrder(String, String, String[])}.
      * </p><p>
      * The specified key may either refer to a simple key or be the concatenation of the
      * path of a child node and key. If the key contains a slash ("/") character, then a
      * double-slash must be used to denote the end of they child path and the beginning
      * of the key. Otherwise it is assumed that the key is the last segment of the path.
      * The following are some examples of keys and their meanings:
      * <ul>
      * <li>"a" - look for a value for the property "a"
      * <li>"//a" - look for a value for the property "a"
      * <li>"///a" - look for a value for the property "/a"
      * <li>"//a//b" - look for a value for the property "a//b"
      * <li>"a/b/c" - look in the child node "a/b" for property "c"
      * <li>"/a/b/c" - look in the child node "a/b" for property "c"
      * <li>"/a/b//c" - look in the child node "a/b" for the property "c"
      * <li>"a/b//c/d" - look in the child node "a/b" for the property "c/d"
      * <li>"/a/b//c/d" - look in the child node "a/b" for the property "c/d"
      * <li>"/a/b//c//d" - look in the child node "a/b" for the property "c//d"
      * </ul>
      * </p><p>
      * Callers may specify an array of scope context objects to aid in the
      * determination of the correct nodes. For each entry in the lookup
      * order, the array of contexts is consulted and if one matching the
      * scope exists, then it is used to calculate the node. Otherwise a
      * default calculation algorithm is used.
      * </p><p>
      * An example of a qualifier for an Eclipse 2.1 preference is the
      * plug-in identifier. (e.g. "org.eclipse.core.resources" for "description.autobuild")
      * </p>
      * @param qualifier a namespace qualifier for the preference
      * @param key the name of the preference (optionally including its path)
      * @param defaultValue the value to use if the preference is not defined
      * @param contexts optional context objects to help scopes determine which nodes to search, or <code>null</code>
      * @return the value of the preference or the given default value
      * @see IScopeContext
      * @see #get(java.lang.String, java.lang.String, org.osgi.service.prefs.Preferences[])
      * @see #getLookupOrder(java.lang.String, java.lang.String)
      * @see #getDefaultLookupOrder(java.lang.String, java.lang.String)
      */
     public boolean getBoolean(String qualifier, String key, boolean defaultValue, IScopeContext[] contexts);

     /**
      * Return the value stored in the preference store for the given key.
      * If the key is not defined then return the specified default value.
      * Use the canonical scope lookup order for finding the preference value.
      * <p>
      * The semantics of this method are to calculate the appropriate
      * {@link Preferences} nodes in the preference hierarchy to use
      * and then call the {@link #get(String, String, Preferences[])}
      * method. The order of the nodes is calculated by consulting the default
      * scope lookup order as set by {@link #setDefaultLookupOrder(String, String, String[])}.
      * </p><p>
      * The specified key may either refer to a simple key or be the concatenation of the
      * path of a child node and key. If the key contains a slash ("/") character, then a
      * double-slash must be used to denote the end of they child path and the beginning
      * of the key. Otherwise it is assumed that the key is the last segment of the path.
      * The following are some examples of keys and their meanings:
      * <ul>
      * <li>"a" - look for a value for the property "a"
      * <li>"//a" - look for a value for the property "a"
      * <li>"///a" - look for a value for the property "/a"
      * <li>"//a//b" - look for a value for the property "a//b"
      * <li>"a/b/c" - look in the child node "a/b" for property "c"
      * <li>"/a/b/c" - look in the child node "a/b" for property "c"
      * <li>"/a/b//c" - look in the child node "a/b" for the property "c"
      * <li>"a/b//c/d" - look in the child node "a/b" for the property "c/d"
      * <li>"/a/b//c/d" - look in the child node "a/b" for the property "c/d"
      * <li>"/a/b//c//d" - look in the child node "a/b" for the property "c//d"
      * </ul>
      * </p><p>
      * Callers may specify an array of scope context objects to aid in the
      * determination of the correct nodes. For each entry in the lookup
      * order, the array of contexts is consulted and if one matching the
      * scope exists, then it is used to calculate the node. Otherwise a
      * default calculation algorithm is used.
      * </p><p>
      * An example of a qualifier for an Eclipse 2.1 preference is the
      * plug-in identifier. (e.g. "org.eclipse.core.resources" for "description.autobuild")
      * </p>
      * @param qualifier a namespace qualifier for the preference
      * @param key the name of the preference (optionally including its path)
      * @param defaultValue the value to use if the preference is not defined
      * @param contexts optional context objects to help scopes determine which nodes to search, or <code>null</code>
      * @return the value of the preference or the given default value
      * @see IScopeContext
      * @see #get(java.lang.String, java.lang.String, org.osgi.service.prefs.Preferences[])
      * @see #getLookupOrder(java.lang.String, java.lang.String)
      * @see #getDefaultLookupOrder(java.lang.String, java.lang.String)
      */
     public byte[] getByteArray(String qualifier, String key, byte[] defaultValue, IScopeContext[] contexts);

     /**
      * Return the value stored in the preference store for the given key.
      * If the key is not defined then return the specified default value.
      * Use the canonical scope lookup order for finding the preference value.
      * <p>
      * The semantics of this method are to calculate the appropriate
      * {@link Preferences} nodes in the preference hierarchy to use
      * and then call the {@link #get(String, String, Preferences[])}
      * method. The order of the nodes is calculated by consulting the default
      * scope lookup order as set by {@link #setDefaultLookupOrder(String, String, String[])}.
      * </p><p>
      * The specified key may either refer to a simple key or be the concatenation of the
      * path of a child node and key. If the key contains a slash ("/") character, then a
      * double-slash must be used to denote the end of they child path and the beginning
      * of the key. Otherwise it is assumed that the key is the last segment of the path.
      * The following are some examples of keys and their meanings:
      * <ul>
      * <li>"a" - look for a value for the property "a"
      * <li>"//a" - look for a value for the property "a"
      * <li>"///a" - look for a value for the property "/a"
      * <li>"//a//b" - look for a value for the property "a//b"
      * <li>"a/b/c" - look in the child node "a/b" for property "c"
      * <li>"/a/b/c" - look in the child node "a/b" for property "c"
      * <li>"/a/b//c" - look in the child node "a/b" for the property "c"
      * <li>"a/b//c/d" - look in the child node "a/b" for the property "c/d"
      * <li>"/a/b//c/d" - look in the child node "a/b" for the property "c/d"
      * <li>"/a/b//c//d" - look in the child node "a/b" for the property "c//d"
      * </ul>
      * </p><p>
      * Callers may specify an array of scope context objects to aid in the
      * determination of the correct nodes. For each entry in the lookup
      * order, the array of contexts is consulted and if one matching the
      * scope exists, then it is used to calculate the node. Otherwise a
      * default calculation algorithm is used.
      * </p><p>
      * An example of a qualifier for an Eclipse 2.1 preference is the
      * plug-in identifier. (e.g. "org.eclipse.core.resources" for "description.autobuild")
      * </p>
      * @param qualifier a namespace qualifier for the preference
      * @param key the name of the preference (optionally including its path)
      * @param defaultValue the value to use if the preference is not defined
      * @param contexts optional context objects to help scopes determine which nodes to search, or <code>null</code>
      * @return the value of the preference or the given default value
      * @see IScopeContext
      * @see #get(java.lang.String, java.lang.String, org.osgi.service.prefs.Preferences[])
      * @see #getLookupOrder(java.lang.String, java.lang.String)
      * @see #getDefaultLookupOrder(java.lang.String, java.lang.String)
      */
     public double getDouble(String qualifier, String key, double defaultValue, IScopeContext[] contexts);

     /**
      * Return the value stored in the preference store for the given key.
      * If the key is not defined then return the specified default value.
      * Use the canonical scope lookup order for finding the preference value.
      * <p>
      * The semantics of this method are to calculate the appropriate
      * {@link Preferences} nodes in the preference hierarchy to use
      * and then call the {@link #get(String, String, Preferences[])}
      * method. The order of the nodes is calculated by consulting the default
      * scope lookup order as set by {@link #setDefaultLookupOrder(String, String, String[])}.
      * </p><p>
      * The specified key may either refer to a simple key or be the concatenation of the
      * path of a child node and key. If the key contains a slash ("/") character, then a
      * double-slash must be used to denote the end of they child path and the beginning
      * of the key. Otherwise it is assumed that the key is the last segment of the path.
      * The following are some examples of keys and their meanings:
      * <ul>
      * <li>"a" - look for a value for the property "a"
      * <li>"//a" - look for a value for the property "a"
      * <li>"///a" - look for a value for the property "/a"
      * <li>"//a//b" - look for a value for the property "a//b"
      * <li>"a/b/c" - look in the child node "a/b" for property "c"
      * <li>"/a/b/c" - look in the child node "a/b" for property "c"
      * <li>"/a/b//c" - look in the child node "a/b" for the property "c"
      * <li>"a/b//c/d" - look in the child node "a/b" for the property "c/d"
      * <li>"/a/b//c/d" - look in the child node "a/b" for the property "c/d"
      * <li>"/a/b//c//d" - look in the child node "a/b" for the property "c//d"
      * </ul>
      * </p><p>
      * Callers may specify an array of scope context objects to aid in the
      * determination of the correct nodes. For each entry in the lookup
      * order, the array of contexts is consulted and if one matching the
      * scope exists, then it is used to calculate the node. Otherwise a
      * default calculation algorithm is used.
      * </p><p>
      * An example of a qualifier for an Eclipse 2.1 preference is the
      * plug-in identifier. (e.g. "org.eclipse.core.resources" for "description.autobuild")
      * </p>
      * @param qualifier a namespace qualifier for the preference
      * @param key the name of the preference (optionally including its path)
      * @param defaultValue the value to use if the preference is not defined
      * @param contexts optional context objects to help scopes determine which nodes to search, or <code>null</code>
      * @return the value of the preference or the given default value
      * @see IScopeContext
      * @see #get(java.lang.String, java.lang.String, org.osgi.service.prefs.Preferences[])
      * @see #getLookupOrder(java.lang.String, java.lang.String)
      * @see #getDefaultLookupOrder(java.lang.String, java.lang.String)
      */
     public float getFloat(String qualifier, String key, float defaultValue, IScopeContext[] contexts);

     /**
      * Return the value stored in the preference store for the given key.
      * If the key is not defined then return the specified default value.
      * Use the canonical scope lookup order for finding the preference value.
      * <p>
      * The semantics of this method are to calculate the appropriate
      * {@link Preferences} nodes in the preference hierarchy to use
      * and then call the {@link #get(String, String, Preferences[])}
      * method. The order of the nodes is calculated by consulting the default
      * scope lookup order as set by {@link #setDefaultLookupOrder(String, String, String[])}.
      * </p><p>
      * The specified key may either refer to a simple key or be the concatenation of the
      * path of a child node and key. If the key contains a slash ("/") character, then a
      * double-slash must be used to denote the end of they child path and the beginning
      * of the key. Otherwise it is assumed that the key is the last segment of the path.
      * The following are some examples of keys and their meanings:
      * <ul>
      * <li>"a" - look for a value for the property "a"
      * <li>"//a" - look for a value for the property "a"
      * <li>"///a" - look for a value for the property "/a"
      * <li>"//a//b" - look for a value for the property "a//b"
      * <li>"a/b/c" - look in the child node "a/b" for property "c"
      * <li>"/a/b/c" - look in the child node "a/b" for property "c"
      * <li>"/a/b//c" - look in the child node "a/b" for the property "c"
      * <li>"a/b//c/d" - look in the child node "a/b" for the property "c/d"
      * <li>"/a/b//c/d" - look in the child node "a/b" for the property "c/d"
      * <li>"/a/b//c//d" - look in the child node "a/b" for the property "c//d"
      * </ul>
      * </p><p>
      * Callers may specify an array of scope context objects to aid in the
      * determination of the correct nodes. For each entry in the lookup
      * order, the array of contexts is consulted and if one matching the
      * scope exists, then it is used to calculate the node. Otherwise a
      * default calculation algorithm is used.
      * </p><p>
      * An example of a qualifier for an Eclipse 2.1 preference is the
      * plug-in identifier. (e.g. "org.eclipse.core.resources" for "description.autobuild")
      * </p>
      * @param qualifier a namespace qualifier for the preference
      * @param key the name of the preference (optionally including its path)
      * @param defaultValue the value to use if the preference is not defined
      * @param contexts optional context objects to help scopes determine which nodes to search, or <code>null</code>
      * @return the value of the preference or the given default value
      * @see IScopeContext
      * @see #get(java.lang.String, java.lang.String, org.osgi.service.prefs.Preferences[])
      * @see #getLookupOrder(java.lang.String, java.lang.String)
      * @see #getDefaultLookupOrder(java.lang.String, java.lang.String)
      */
     public int getInt(String qualifier, String key, int defaultValue, IScopeContext[] contexts);

     /**
      * Return the value stored in the preference store for the given key.
      * If the key is not defined then return the specified default value.
      * Use the canonical scope lookup order for finding the preference value.
      * <p>
      * The semantics of this method are to calculate the appropriate
      * {@link Preferences} nodes in the preference hierarchy to use
      * and then call the {@link #get(String, String, Preferences[])}
      * method. The order of the nodes is calculated by consulting the default
      * scope lookup order as set by {@link #setDefaultLookupOrder(String, String, String[])}.
      * </p><p>
      * The specified key may either refer to a simple key or be the concatenation of the
      * path of a child node and key. If the key contains a slash ("/") character, then a
      * double-slash must be used to denote the end of they child path and the beginning
      * of the key. Otherwise it is assumed that the key is the last segment of the path.
      * The following are some examples of keys and their meanings:
      * <ul>
      * <li>"a" - look for a value for the property "a"
      * <li>"//a" - look for a value for the property "a"
      * <li>"///a" - look for a value for the property "/a"
      * <li>"//a//b" - look for a value for the property "a//b"
      * <li>"a/b/c" - look in the child node "a/b" for property "c"
      * <li>"/a/b/c" - look in the child node "a/b" for property "c"
      * <li>"/a/b//c" - look in the child node "a/b" for the property "c"
      * <li>"a/b//c/d" - look in the child node "a/b" for the property "c/d"
      * <li>"/a/b//c/d" - look in the child node "a/b" for the property "c/d"
      * <li>"/a/b//c//d" - look in the child node "a/b" for the property "c//d"
      * </ul>
      * </p><p>
      * Callers may specify an array of scope context objects to aid in the
      * determination of the correct nodes. For each entry in the lookup
      * order, the array of contexts is consulted and if one matching the
      * scope exists, then it is used to calculate the node. Otherwise a
      * default calculation algorithm is used.
      * </p><p>
      * An example of a qualifier for an Eclipse 2.1 preference is the
      * plug-in identifier. (e.g. "org.eclipse.core.resources" for "description.autobuild")
      * </p>
      * @param qualifier a namespace qualifier for the preference
      * @param key the name of the preference (optionally including its path)
      * @param defaultValue the value to use if the preference is not defined
      * @param contexts optional context objects to help scopes determine which nodes to search, or <code>null</code>
      * @return the value of the preference or the given default value
      * @see IScopeContext
      * @see #get(java.lang.String, java.lang.String, org.osgi.service.prefs.Preferences[])
      * @see #getLookupOrder(java.lang.String, java.lang.String)
      * @see #getDefaultLookupOrder(java.lang.String, java.lang.String)
      */
     public long getLong(String qualifier, String key, long defaultValue, IScopeContext[] contexts);

     /**
      * Return the value stored in the preference store for the given key.
      * If the key is not defined then return the specified default value.
      * Use the canonical scope lookup order for finding the preference value.
      * <p>
      * The semantics of this method are to calculate the appropriate
      * {@link Preferences} nodes in the preference hierarchy to use
      * and then call the {@link #get(String, String, Preferences[])}
      * method. The order of the nodes is calculated by consulting the default
      * scope lookup order as set by {@link #setDefaultLookupOrder(String, String, String[])}.
      * </p><p>
      * The specified key may either refer to a simple key or be the concatenation of the
      * path of a child node and key. If the key contains a slash ("/") character, then a
      * double-slash must be used to denote the end of they child path and the beginning
      * of the key. Otherwise it is assumed that the key is the last segment of the path.
      * The following are some examples of keys and their meanings:
      * <ul>
      * <li>"a" - look for a value for the property "a"
      * <li>"//a" - look for a value for the property "a"
      * <li>"///a" - look for a value for the property "/a"
      * <li>"//a//b" - look for a value for the property "a//b"
      * <li>"a/b/c" - look in the child node "a/b" for property "c"
      * <li>"/a/b/c" - look in the child node "a/b" for property "c"
      * <li>"/a/b//c" - look in the child node "a/b" for the property "c"
      * <li>"a/b//c/d" - look in the child node "a/b" for the property "c/d"
      * <li>"/a/b//c/d" - look in the child node "a/b" for the property "c/d"
      * <li>"/a/b//c//d" - look in the child node "a/b" for the property "c//d"
      * </ul>
      * </p><p>
      * Callers may specify an array of scope context objects to aid in the
      * determination of the correct nodes. For each entry in the lookup
      * order, the array of contexts is consulted and if one matching the
      * scope exists, then it is used to calculate the node. Otherwise a
      * default calculation algorithm is used.
      * </p><p>
      * An example of a qualifier for an Eclipse 2.1 preference is the
      * plug-in identifier. (e.g. "org.eclipse.core.resources" for "description.autobuild")
      * </p>
      * @param qualifier a namespace qualifier for the preference
      * @param key the name of the preference (optionally including its path)
      * @param defaultValue the value to use if the preference is not defined
      * @param contexts optional context objects to help scopes determine which nodes to search, or <code>null</code>
      * @return the value of the preference or the given default value
      * @see IScopeContext
      * @see #get(java.lang.String, java.lang.String, org.osgi.service.prefs.Preferences[])
      * @see #getLookupOrder(java.lang.String, java.lang.String)
      * @see #getDefaultLookupOrder(java.lang.String, java.lang.String)
      */
     public String getString(String qualifier, String key, String defaultValue, IScopeContext[] contexts);

     /**
      * Return the root node of the Eclipse preference hierarchy.
      *
      * @return the root of the hierarchy
      */
     public IEclipsePreferences getRootNode();

     /**
      * Exports all preferences for the given preference node and all its children to the specified
      * output stream. It is the responsibility of the client to close the given output stream.
      * <p>
      * If the given export list is <code>null</code> then all preferences for all sub-nodes
      * of the given node are exported to the given stream. Otherwise the export list is
      * consulted before exporting each preference value. If there is a string match then
      * the preference is not exported. The exclusion can also occur at a per-node level.
      * Wild cards are <em>not</em> accepted in the excludes list as a basic String compare
      * is done. The basic algorithm is similar to the following:
      * <pre>
      * String fullPath = node.absolutePath() + '/' + key;
      * if (!fullPath.startsWith(excludesList[i]))
      * // export preference
      * </pre>
      * </p>
      * <p>
      * The values stored in the resulting stream are suitable for later being read by the
      * by {@link #importPreferences(InputStream)} or {@link #readPreferences(InputStream)} methods.
      * </p>
      * @param node the node to treat as the root of the export
      * @param output the stream to write to
      * @param excludesList a list of path prefixes to exclude from the export, or <code>null</code>
      * @return a status object describing success or detailing failure reasons
      * @throws CoreException if there was a problem exporting the preferences
      * @throws IllegalArgumentException if the node or stream is <code>null</code>
      * @see #importPreferences(java.io.InputStream)
      * @see #readPreferences(InputStream)
      */
     public IStatus exportPreferences(IEclipsePreferences node, OutputStream output, String [] excludesList) throws CoreException;

     /**
      * Loads preferences from the given file and stores them in the preferences store.
      * Existing values are over-ridden by those from the stream. The stream must not be
      * <code>null</code> and is closed upon return from this method.
      * <p>
      * This file must have been written by the
      * {@link #exportPreferences(IEclipsePreferences, OutputStream, String[])}
      * method.
      * </p>
      * <p>
      * This method is equivalent to calling <code>applyPreferences(readPreferences(input));</code>.
      * </p>
      * @param input the stream to load the preferences from
      * @return a status object describing success or detailing failure reasons
      * @throws CoreException if there are problems importing the preferences
      * @throws IllegalArgumentException if the stream is <code>null</code>
      * @see #exportPreferences(IEclipsePreferences, OutputStream, String[])
      */
     public IStatus importPreferences(InputStream input) throws CoreException;

     /**
      * Take the given preference tree and apply it to the Eclipse
      * global preference hierarchy. If a node is an export root, then
      * remove it from the global tree before adding any preferences
      * contained in it or its children. The given preferences object
      * must not be <code>null</code>.
      * <p>
      * Before the tree is applied to the global preference tree,
      * the registered <code>PreferenceModifyListener</code> objects
      * are called and given the opportunity to modify the tree.
      * </p>
      *
      * @param preferences the preferences to apply globally
      * @return status object indicating success or failure
      * @throws IllegalArgumentException if the preferences are <code>null</code>
      * @throws CoreException if there are problems applying the preferences
      * @see PreferenceModifyListener
      */
     public IStatus applyPreferences(IExportedPreferences preferences) throws CoreException;

     /**
      * Read from the given input stream and create a node hierarchy
      * representing the preferences and their values. The given input stream
      * must not be <code>null</code>. The result of this function is suitable
      * for passing as an argument to {@link #applyPreferences(IExportedPreferences)}.
      * <p>
      * It is assumed the contents of the input stream have been written by
      * {@link #exportPreferences(IEclipsePreferences, OutputStream, String[])}.
      * </p>
      * @param input the input stream to read from
      * @return the node hierarchy representing the stream contents
      * @throws IllegalArgumentException if the given stream is null
      * @throws CoreException if there are problems reading the preferences
      * @see #exportPreferences(IEclipsePreferences, OutputStream, String[])
      * @see #applyPreferences(IExportedPreferences)
      */
     public IExportedPreferences readPreferences(InputStream input) throws CoreException;

     /**
      * Return an array with the default lookup order for the preference keyed by the given
      * qualifier and simple name. Return <code>null</code> if no default has been set.
      * <p>
      * The lookup order returned is based on an exact match to the specified qualifier
      * and simple name. For instance, if the given key is non-<code>null</code> and
      * no default lookup order is found, the default lookup order for the qualifier (and a
      * <code>null</code> key) is <em>NOT</em> returned. Clients should call
      * {@link #getLookupOrder(String, String)} if they desire this behavior.
      * </p>
      * @param qualifier the namespace qualifier for the preference
      * @param key the preference name or <code>null</code>
      * @return the scope order or <code>null</code>
      * @see #setDefaultLookupOrder(String, String, String[])
      * @see #getLookupOrder(String, String)
      */
     public String [] getDefaultLookupOrder(String qualifier, String key);

     /**
      * Return an array with the lookup order for the preference keyed by the given
      * qualifier and simple name.
      * <p>
      * First do an exact match lookup with the given qualifier and simple name. If a match
      * is found then return it. Otherwise if the key is non-<code>null</code> then
      * do a lookup based on only the qualifier and return the set value.
      * Return the default-default order as defined by the platform if no order has been set.
      * </p>
      * @param qualifier the namespace qualifier for the preference
      * @param key the preference name or <code>null</code>
      * @return the scope order
      * @throws IllegalArgumentException if the qualifier is <code>null</code>
      * @see #getDefaultLookupOrder(String, String)
      * @see #setDefaultLookupOrder(String, String, String[])
      */
     public String [] getLookupOrder(String qualifier, String key);

     /**
      * Set the default scope lookup order for the preference keyed by the given
      * qualifier and simple name. If the given order is <code>null</code> then the set
      * ordering (if it exists) is removed.
      * <p>
      * If the given simple name is <code>null</code> then set the given lookup
      * order to be used for all keys with the given qualifier.
      * </p><p>
      * Note that the default lookup order is not persisted across platform invocations.
      * </p>
      * @param qualifier the namespace qualifier for the preference
      * @param key the preference name or <code>null</code>
      * @param order the lookup order or <code>null</code>
      * @throws IllegalArgumentException
      * <ul>
      * <li>if the qualifier is <code>null</code></li>
      * <li>if an entry in the order array is <code>null</code> (the array itself is
      * allowed to be <code>null</code></li>
      * </ul>
      * @see #getDefaultLookupOrder(String, String)
      */
     public void setDefaultLookupOrder(String qualifier, String key, String [] order);

     /**
      * Export the preference tree rooted at the given node, to the specified output
      * stream. Apply the given list of preference filters, only exporting
      * preference node and keys which are applicable to at least one filter in the list.
      * <p>
      * The given node and output stream must not be <code>null</code>.
      * If the list of filters is <code>null</code> or empty then do nothing.
      * </p>
      * <p>
      * It is the responsibility of the client to close the given output stream.
      * </p>
      *
      * @param node the tree to export
      * @param filters the list of filters to export
      * @param output the stream to export to
      * @throws CoreException
      * @see #exportPreferences(IEclipsePreferences, OutputStream, String[])
      * @see #readPreferences(InputStream)
      * @see #applyPreferences(IEclipsePreferences, IPreferenceFilter[])
      * @see #applyPreferences(IExportedPreferences)
      * @see IPreferenceFilter
      * @since 3.1
      */
     public void exportPreferences(IEclipsePreferences node, IPreferenceFilter[] filters, OutputStream output) throws CoreException;

     /**
      * Return a list of filters which match the given tree and is a subset of the given
      * filter list. If the specified list of filters is <code>null</code>, empty, or there
      * are no matches, then return an empty list.
      *
      * @param node the tree to match against
      * @param filters the list of filters to match against
      * @return the array of matching transfers
      * @throws CoreException
      * @see IPreferenceFilter
      * @since 3.1
      */
     public IPreferenceFilter[] matches(IEclipsePreferences node, IPreferenceFilter[] filters) throws CoreException;

     /**
      * Apply the preference tree rooted at the given node, to the system's preference tree.
      * The list of preference filters will act as a filter and only preferences in the tree which
      * apply to at least one filter in the list, will be applied.
      * <p>
      * If the list of filters is <code>null</code> or empty then do nothing.
      * </p>
      * <p>
      * Before the tree is applied to the global preference tree,
      * the registered <code>PreferenceModifyListener</code> objects
      * are called and given the opportunity to modify the tree.
      * </p>
      *
      * @param node the tree to consider applying
      * @param filters the filters to use
      * @throws CoreException
      * @see #applyPreferences(IExportedPreferences)
      * @see #readPreferences(InputStream)
      * @see IPreferenceFilter
      * @see PreferenceModifyListener
      * @since 3.1
      */
     public void applyPreferences(IEclipsePreferences node, IPreferenceFilter[] filters) throws CoreException;
 }

